Rayleigh-Brillouin scattering from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si64.svg" display="inline" id="d1e469"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si65.svg" display="inline" id="d1e489"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">CH</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> mixtures at elevated pressures
Bibliographic record
Abstract
This paper presents spectral measurements of Rayleigh-Brillouin scattering (RBS) spectra in binary mixtures of H2/N2 and H2/CH4 at a number of mixture ratios at 300 K, and pressures ranging from 4 to 60 atm. To identify trends in lineshape changes associated with H2 addition, measured spectra of pure N2 and CH4 at 300 K and similar pressures are included. These measurements were acquired with a custom spectrometer based on an air-spaced virtually-imaged phased array whose resolving power was on the order of 107λ/Δλ. Improvements upon previous work to the data processing procedure, including revised implementation of the scalar envelope correction, and the addition of a dispersion correction, are described. Measurements of RBS spectra in pure N2 and CH4 are compared to their counterparts modelled by Tenti S6. Good agreement is observed in pressures up to 20 atm, and discrepancies at higher pressure are attributable to known limitations in the measurements and model. Attenuation and broadening of the Brillouin and central Rayleigh peaks, as well as an outward shift of the Brillouin doublet, are observed with H2 addition. These trends are related to the dissipative role of H2 on thermodynamic fluctuations in the fluid medium, enhanced by its mass disparity with the host species. Analysis of spectral energy distribution in mixture spectra at 20+ atm reveals a net transfer of spectral energy from the Brillouin doublet towards the central Rayleigh peak with increasing H2 dilution. Experimental and modelled RBS spectra, and a model I2 filter, are used to test the validity, at elevated pressure, of approximating a mixture filtered Rayleigh scattering (FRS) signal by a mole fraction-weighted sum of isolated FRS signals from mixture constituents. FRS signals calculated from measured mixture spectra are compared to their approximations calculated from modelled pure gas spectra. Results show limited and inconsistent agreement. Where agreement is strong, further analysis reveals a sensitive counterbalance of factors affecting FRS signal generation that is not reliable for robust FRS signal inversion. The work demonstrates the need for improved spectral models to support the application of FRS diagnostics to fluid mixtures at elevated pressure.
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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 | 0.011 | 0.008 |
| Meta-epidemiology (narrow) | 0.006 | 0.013 |
| Meta-epidemiology (broad) | 0.002 | 0.010 |
| Bibliometrics | 0.004 | 0.008 |
| Science and technology studies | 0.010 | 0.011 |
| Scholarly communication | 0.011 | 0.012 |
| Open science | 0.015 | 0.014 |
| Research integrity | 0.015 | 0.012 |
| Insufficient payload (model declined to judge) | 0.875 | 0.009 |
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; both teacher heads agree on what is shown here.
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".