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Uncertainty quantification and design-of-experiment in absorption-based aqueous film parameter measurements using
This study uses near-infrared absorption and Bayesian analysis to simultaneously measure aqueous film thickness, temperature, and urea concentration. This advanced method provides accurate, real-time data for dynamic processes like evaporation.
Area of Science:
- Spectroscopy
- Chemical Sensing
- Physical Chemistry
Background:
- Near-infrared (NIR) absorption spectroscopy offers potential for simultaneous, time-resolved measurements of aqueous film properties.
- Previous research could only determine two parameters (thickness, temperature, or concentration) at a time, requiring a third to be fixed.
- Accurate, simultaneous measurement of multiple parameters is crucial for understanding dynamic processes in thin films.
Purpose of the Study:
- To develop and validate a method for simultaneous, multi-parameter measurement of film thickness, temperature, and solute (urea) concentration using NIR absorption.
- To integrate Bayesian methodology with NIR spectroscopy for robust data analysis and uncertainty quantification.
- To demonstrate the technique's application in a real-world scenario, such as film evaporation.
Main Methods:
- Utilized diode laser-based multi-wavelength NIR absorption spectroscopy.
- Generated a comprehensive spectral database of water with varying temperature and urea concentration (5500–8000 cm⁻¹).
- Employed Bayesian analysis with a Markov chain Monte Carlo (MCMC) algorithm to infer probability densities and credibility intervals for measured parameters.
Main Results:
- Successfully demonstrated simultaneous measurement of film thickness, temperature, and urea concentration.
- Validated the method using a calibration cell.
- Quantified parameter uncertainties using probability densities derived from MCMC analysis.
- Recorded temporal variations of all three parameters during the evaporation of a liquid film.
Conclusions:
- The combined NIR absorption spectroscopy and Bayesian analysis approach enables accurate, simultaneous determination of film thickness, temperature, and solute concentration.
- This technique provides a powerful tool for real-time monitoring of dynamic processes in aqueous films.
- The method's ability to quantify uncertainties enhances its reliability for scientific and industrial applications.
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