ntfit 2.1.0

nonuniform-temperature fitting

Non-uniform Temperature Fitting (NTfit)

Nonuniform-temperature fitting code, to extract spatial temperature variations along a laser path. For high-temperature gas diagnostics.

In support of the 2-part paper series N.A. Malarich and G.B. Rieker, "Resolving nonuniform temperature distributions with single-beam absorption spectroscopy"

Nonuniform-temperature fitting is a two-step process. The Python package ntfit has sub-packages for each step.

1. ntfit.spectrafit: Extract linestrengths from broadband spectrum with E"-binning.
2. ntfit.tdist: Fit temperature distribution from linestrength fit in (1) with Tikhonov regularization.

For help running the fits, check out examples/Example_td.py, or the associated .ipynb (Jupyter Notebook) file.

Package requirements

Your computer must already have the following Python packages:

python3.x
numpy
matplotlib
scipy

NTfit also includes HAPI, available under MIT license. NTfit changed HAPI version 1.1.0.9.6 lineshape equations (power-law temperature dependence) from original HAPI to improve high-temperature acuracy. See ntfit/hapi/hapi_combustion.py docstring for details. Partition functions are calculated using TIPS2017.

References

If you use this package, please cite the following articles. for E"-bin fitting with HAPI:

• R.V. Kochanov, I.E. Gordon, L.S. Rothman, P. Wcislo, C. Hill, J.S. Wilzewski, HITRAN Application Programming Interface (HAPI): A comprehensive approach to working with spectroscopic data, J. Quant. Spectrosc. Radiat. Transfer 177, 15-30 (2016) DOI: 10.1016/j.jqsrt.2016.03.005.

• N.A. Malarich and G.B. Rieker, "Resolving nonuniform temperature distributions with single-beam absorption spectroscopy. Part II: Implementation from broadband spectra" JQSRT (2021) DOI: 10.1016/j.jqsrt.2021.107805

• (time-domain fitting) R.K. Cole, A.S. Makowiecki, Z. Hoghooghi, G.B. Rieker, "Baseline-free Quantitative Absorption Spectroscopy Based on Cepstral Analysis" Optics Express 27 (2019) DOI: 10.1364/OE.27.037920.

for ntfit.tdist:

• N.A. Malarich and G.B. Rieker, "Resolving nonuniform temperature distributions with single-beam absorption spectroscopy. Part I: Theoretical capabilities and limitations" JQSRT (2021) DOI: 10.1016/j.jqsrt.2020.107455

Author

Nathan Malarich ([e-mail])

Change Log

[2.1] - 2022-09-23

Changed

• ntfit now a separate sub-package, compatible with pip install
• hapi sub-package has separate file for Q(T) tables
• Removed uniform_fit example, as lookup table is much more efficient way to fit temperature
• Tikhonov regularization module now ntfit.tdist
• E"-bin spectral-fitting now ntfit.spectrafit

[2.0] - 2021-03-01

Added

• E"-bin spectral fitting package with hapi